1. Field of the Invention
This invention relates to an apparatus for dispensing and applying finely divided particulate or granular matter on a tacky surface. More particularly this invention relates to a device for breaking up particle aggregates by utilizing a sieving operation and assuring a controlled and uniform dispensing and deposition of said material.
While the apparatus of this invention is of general utility in the dispensing of finely divided particulate matter, it is particularly well suited for dispensing a uniform layer of toner on an imagewise exposed photohardenable layer.
2. Description of the Prior Art
A number of devices have been developed to apply toner on an imagewise exposed surface as a result of the wide commercial acceptance of electrophotography. Thus, a variety of devices and techniques are known for applying electroscopic powders.
U.S. Pat. No. 3,374,768 discloses a developing apparatus which employs a powder cloud for developing electrostatic images formed on a photoconductive surface. The use of such an apparatus, however, can create an ambient dust problem and necessitates the use of expensive dust removal systems.
When a transfer roll type toner application system is used, it is known in the art to use a hopper from which a quantity of toner is transferred to an intermediate or dispensing roller prior to pick up by an applicator roller. Such an intermediate roller is usually provided with scoops on its outside surface which helps transfer a fixed quantity of toner from the hopper to the applicator roller.
This procedure of transferring a fixed quantity of toner using an intermediate or dispensing roller provided with scoops on its outer surface is disclosed in U.S. Pat. No. 3,622,054. The toner is transferred from a flaccid, baglike container to a supply of developer material using said intermediate roll. A frictionally driver brush roll provided with semirigid bristles is used to prevent the agglomeration of the toner powder or bridging of the powder above the dispensing roll.
In U.S. Pat. No. 3,125,465 a sheet duster comprising an applicator roll and a transfer roll which transfers a powdered lubricant from a supply bin or hopper to the applicator roll is disclosed. The supply bin is vibrated to prevent the formation of particle agglomerates. This apparatus however would have to be used in a closed environment where special means are available to avoid powdered lubricant from spreading over the work area. U.S. Pat. Nos. 3,532,071 and 3,592,725 also disclose particle application to a surface.
In the application of a toner on an exposed, photohardenable layer, advantage is taken of the difference in adhesion between areas exposed to actinic radiation and non-exposed areas, to render an image visible. A simple device is needed which will reproducibly apply a substantially uniform toner layer so as to produce a toned area without streaks and mottle.
The need for a simple and inexpensive device to do this is greater when a multicolored image is to be reproduced, where toner layers of different colors are to be used in sequence as described in U.S. Pat. No. 3,649,268. In addition, most of the prior art devices are intended for use in a closed environment such as inside a machine, where special means are available to avoid toner dust from spreading over the work area. There is need for a simple toner applicator which can apply toner without generating a dust cloud and which can be used by an operator without special dust removing or filtering means.